"The Soul is the friend of Self and also its enemy; and, that a man should raise the self by the self." This book is meant for sincere students, and especially for those who have some glimmering of what Krishna meant, when in Bhagavad-Gita he said, that after a while spiritual knowledge grows up within and illuminates with its rays all subjects and objects. Patanjali's rules compel the student not only to acquire a right knowledge of what is and what is not real, but also to practice all virtues.